How come video splitting is such a slow process?

Hello,

I am in need of a fast video splitting software.
I have tried lots of different applications but they all take a lot of time to publish the video's you have trimmed.
Why is this such a slow process? Trimming little bits of video at the start/end of a video file should take long, should it?

Someone please enlighten me

Greetz

Edit: I'm sorry, posted in the wrong section. This should be under general software problems.